1. Field of the Invention
The present invention relates to the packaging of products and, more particularly, to the splicing of webs of packaging material which have been wound onto bobbins of cigarette packaging machines. More specifically, the present invention is directed to apparatus for splicing webs of packaging material at normal withdrawal speeds without manual intervention and without any reduction of packaging speed. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
2. Description of the Prior Art
Packaging machines employing one or more supply bobbins for packaging material in web format are well known in the art. In the prior art machines, the web of packaging material is typically unwound from an active supply bobbin at a high rate of speed and routed, via one or more rollers, to a remote location where wrapping of the product to be packaged occurs. Since these packaging machines are typically used near the final station of an assembly line, smooth and efficient operation of the entire assembly line demands that the packaging machine be able to operate with sufficient speed to keep up with the supply of products from the earlier stages of the assembly line. Thus, any slow down of the packaging operation can have adverse consequences on the efficiency of the entire assembly line.
Packaging machines were originally developed for use with a single bobbin for supplying the packaging material. In these machines, the web of packaging material was dispensed from the bobbin until the bobbin was exhausted. One major drawback of the more primitive of these early bobbin-type packaging machines is that the machine would invariably have to be shut down when the web of packaging material became completely unwound from the bobbin. After the packaging machine had been shut down, the empty bobbin could then be removed from the packaging machine and replaced with a fresh bobbin having a new roll of packaging material. Once the new roll of packaging material had been loaded onto the packaging machine, the packaging of products could once again resume at a normal rate. However, as mentioned above, the shut down time of the packaging machine resulted in significant reduction in the efficiency, and a concomitant interruption, of the entire assembly line. Thus, a need existed for a packaging machine in which the web of packaging material could be replaced with a new web of packaging material with little or no stoppage of the packaging process. This need has resulted in the development of packaging machines employing a plurality of bobbins, each having a web of packaging material wound thereon, and a splicing apparatus for automated switch-over to a full bobbin of packaging material when most of the web of packaging material was unwound from the active bobbin.
One device which attempts to achieve bobbin replacement with little or no interruption of the packaging operation is disclosed in German Patent 39 29 981. In this device the transition from the nearly exhausted bobbin of packaging material to a full bobbin is achieved by splicing the leading end of a new web of packaging material on a full bobbin to the web being withdrawn from the nearly exhausted bobbin. In this device, the new web of packaging material to be spliced is held ahead of one or more nipping rollers by a clamping strip and a cut out in an adjacent nipping roller. When splicing is to occur, the clamping strip releases the new web of packaging material and the nipping rollers grip the end of the new web with a friction section. However, in order for effective splicing to occur with the device of German Patent 39 29 981, the operating speed of the packaging machine must be greatly reduced. This speed reduction results in a loss of packaging efficiency, albeit to a lesser degree, in the same manner as experienced with a single bobbin machine. Thus, although this device does reduce the inefficiencies associated with bobbin replacement in packaging machines, it has, by no means, eliminated the problem altogether.